1. Field of the Invention
The present invention relates to an apparatus and a method for correcting a grinding amount of a liquid crystal display panel. In more detail, in cutting liquid crystal display panels formed on a mother substrate having large area into individual unit liquid crystal display panels and grinding the edge of each unit liquid crystal display panel, the present invention relates to an apparatus and a method for correcting a grinding amount of a liquid crystal display panel capable of facilitating measurement and correction of a grinding amount thereof.
2. Discussion of the Related Art
Generally, in a liquid crystal display device, because plural liquid crystal display panels are simultaneously formed by forming thin film transistor array substrates onto a mother substrate having large area, forming color filter substrates onto an another mother substrate and adhering the two mother substrates to each other in order to improve an yield rate, a process for cutting the formed liquid crystal display panels in unit liquid crystal display panels is required.
In general, in cutting of liquid crystal display panels, a predetermined cutting line is formed at the surface of the mother substrate by a wheel having a higher hardness than glass, and a crack is spread through the predetermined cutting line. The liquid crystal display panel will be described in more detail with reference to accompanying drawings.
FIG. 1 is an exemplary view illustrating a sectional view of multiple liquid crystal display panels fabricated by attaching a first mother substrate having thin film transistor array substrates to a second mother substrate having color filter substrates.
As shown in FIG. 1, in the unit liquid crystal display panels, a certain side of the thin film transistor array substrate 1 for a unit cell projects in comparison with the color filter substrate 2. It is because a gate pad portion (not shown) and a data pad portion (not shown) which do not correspond to the range of the color filter substrate 2, are formed at the edge of the thin film transistor array substrate 1.
Accordingly, in forming of the color filter substrate 2 onto the second mother substrate 30, there is a dummy region 31 corresponding to the protrusion area of the thin film transistor array substrate 1 formed on the first mother substrate 20.
In addition, each unit liquid crystal display panel is arranged to use the first and second mother substrates 20, 30 to the utmost i.e., to optimize the use of the area of the mother substrates. It may be differentiated according to models, however, generally each unit liquid crystal display panel is separated from each other as a dummy region 32 in arrangement.
After adhering the first mother substrate 1 to the second mother substrate 2, the unit liquid crystal display panels are respectively cut. In the cutting process the dummy region 31 corresponding to the protrusion area of the array substrate 1 and the dummy region 32 for separating each unit liquid crystal display panel are simultaneously removed.
FIG. 2 is a schematic exemplary view illustrating a plan view of a unit liquid crystal display panel.
As shown in FIG. 2, a unit liquid crystal display panel 10 includes a picture display unit 13 on which liquid crystal cells are arranged as a matrix shape; a gate pad unit for connecting gate line (GL1 to GLm) of the picture display unit 13 with a gate driver integrated circuit (IC) (not shown) for receiving gate signals; and a data pad unit 15 for connecting data line (DL1 to DLn) of the picture display unit 13 with a data driver integrated circuit (IC) (not shown) for receiving picture information. Herein, the gate pad unit 14 and the data pad unit 15 are formed at the edge of the thin film transistor array substrate 1 having protrusions along short and long sides (in comparison with the color filter substrate 2).
Although not shown in detail in drawings, each thin film transistor for switching liquid cells in the unit liquid crystal display panel is installed at a region in which a data line (DL1 to DLn) vertically crosses a gate line (GL1 to GLm). Each pixel electrode for applying an electric field to the liquid cells contacts a respective thin film transistor. A protection layer for protecting the data line (DL1 to DLn), the gate line (GL1 to GLm), the thin film transistors and the electrodes is formed over the entire surface.
A plurality of color filters are formed on the color filter substrate 2 cell regions are separated with a black matrix. Common electrodes, which are opposite electrodes of the pixel electrodes, are formed onto the thin film transistor array substrate 1.
The thin film transistor array substrate 1 and the color filter substrate 2, are separated by a cell-gap in order to have a uniform clearance there between. The substrates 1, 2 are adhered to each other by a sealant (not shown) formed at the edge of the picture display unit 13, and a liquid crystal layer (not shown) is formed in a space (cell-gap) between the thin film transistor array substrate 1 and the color filter substrate 2.
In the meantime, shorting bar (not shown) is formed at the edge of the thin film transistor array substrate 1 in order to cut off static electricity generated in patterning conductive layers on the thin film transistor array substrate 1. The shorting bar has to be removed after cutting the liquid crystal display panels in unit liquid crystal display panels.
Accordingly, after cutting the liquid crystal display panels into unit liquid crystal display panels, the shorting bar is removed by grinding the edge of the unit liquid crystal display panel. In addition, by grinding the edge of the unit liquid crystal display panel, it is possible to prevent the edge of the unit liquid crystal display panel from being broken or separating and to prevent a worker from being injured by the sharp edge of the unit liquid crystal display panel in the process.
The grinding process of the unit liquid crystal display panel will be described in detail with reference to accompanying drawings.
FIG. 3 is an exemplary view illustrating a general grinding apparatus for a liquid crystal display panel. As shown in FIG. 3, a general grinding apparatus for a liquid crystal display panel includes a loading unit 50 for loading a cut unit liquid crystal display panel 10; a grinding unit 53 for receiving the unit liquid crystal display panel 10 from the loading unit 50, and arranging the unit liquid crystal display panel 10 on a grinding board 51 and grinding the edge of the unit liquid crystal display panel 10 with a grinding wheel 52 rotating at the high speed; and an unloading unit 54 for receiving the ground unit liquid crystal display panel 10 from the grinding unit 53 and unloading the unit liquid crystal display panel 10.
FIG. 4 is a flow chart illustrating a method for correcting a grinding amount of the unit liquid crystal display panel 10 ground through the grinding apparatus in FIG. 3.
As shown in FIG. 4, the method includes grinding a unit liquid crystal display panel (S11); removing the ground unit liquid crystal display panel from the grinding apparatus and transferring it to an outside measuring apparatus (S12); measuring a grinding amount of the unit liquid crystal display panel (S13); returning the unit liquid crystal display panel to the grinding apparatus (S14); changing a set value of the grinding apparatus by calculating an error between the measured grinding amount and a reference value (S15); and regrinding the unit liquid crystal display panel by using the changed set value of the grinding apparatus (S16).
The related art methods for measuring and correcting the grinding amount of the liquid crystal display panel will be described in more detail.
First, the edge of the unit liquid crystal display panel 10 is ground through the grinding apparatus in FIG. 3 as shown at step S11.
And, the unit liquid crystal display panel 10 is taken out and transferred to the outside measuring apparatus as shown at step S12.
Herein, in order to take out and transfer the unit liquid crystal display panel 10, a worker has to take the unit liquid crystal display panel 10 out from the grinding apparatus and transfer it to the measuring apparatus manually. The work is intricate, and the unit liquid crystal display panel 10 is exposed to external impact.
Afterward, the grinding amount of the unit liquid crystal display panel 10 is measured as shown at step S13.
Herein, in general, because the worker measures the grinding amount of the unit liquid crystal display panel 10 with the naked eye through a screen of a projector, reliability of measuring is lowered.
Also, the unit liquid crystal display panel 10 is taken out from the measuring apparatus and transferred to the grinding apparatus as shown at step S14.
In addition to problems in transferring the unit liquid crystal display panel 10 to the measuring apparatus, in returning of the unit liquid crystal display panel 10 to the grinding apparatus, the worker has to take out the unit liquid crystal display panel 10 from the measuring apparatus and transfer it to the grinding apparatus manually. The work is similarly intricate and the unit liquid crystal display panel 10 is exposed to external impact.
After calculating an error between the grinding amount measured value of the unit liquid crystal display panel 10 and a reference value, a set value of the grinding apparatus is changed as shown at step S15.
To calculate an error between the grinding amount measured value of the unit liquid crystal display panel 10 and the reference value, because the worker memorizes or writes down the measured value and compares the measured value with the reference value after returning the unit liquid crystal display panel 10 to the grinding apparatus, the measured value may be changed due to mistake of the worker.
In addition, because the worker has to change a set value of the grinding apparatus for each item, e.g., each unit liquid crystal display panel, it is intricate.
By applying the changed set value, the unit liquid crystal display panel 10 is reground as shown at step S16.
Accordingly, as shown in FIG. 5, in the related art apparatus and method, the grinding apparatus 60 and the measuring apparatus 70 are separated from each other. In order to measure and correct a grinding amount after grinding a unit liquid crystal display panel, the unit liquid crystal display panel has to be transferred and returned between the grinding and measuring apparatus as 60, 70, and accordingly the operation processes are intricate. In addition, the unit liquid crystal display panel is exposed to external impact, and reliability of grinding amount is lowered.
As described above, in the related art apparatus and method for correcting the grinding amount of the liquid crystal display panel, in order to take out, transfer and return the unit liquid crystal display panel 10, the worker has to perform all those processes manually, and accordingly the work is intricate and the unit liquid crystal display panel is exposed to external impacts.
In addition, by measuring a grinding amount of a unit liquid crystal display panel with the naked eye through a projector, reliability of measuring is lowered. Also, because the worker memorizes or writes down the measured value and compares it with the reference value after returning the unit liquid crystal display panel to the grinding apparatus, the measured value may be obtained differently due to mistake of the worker.
In addition, because the worker has to change a set value of the grinding apparatus for each item through an error between a grinding amount measured value and a reference value, it is intricate.